1. Field of the Invention
This invention relates to cabinet constructions and in particular to insulative refrigeration apparatus cabinet constructions.
2. Description of the Background Art
An improved refrigeration appliance liner construction is disclosed in U.S. Pat. No. 3,960,631 of Leonard E. Weiss et al., which patent is owned by the assignee hereof. As disclosed therein, a foam release agent is provided on the plastic liner sheet prior to the forming thereof into the liner configuration. The foam release agent comprises a film laminated to the liner sheet as by utilizing the heat of extrusion of the liner sheet with concurrent application of pressure. The disclosed film comprises a coextruded film including a first sheet of unmodified low density polyethylene and a sheet of ethylene acrylic acid copolymer which is electrostatically treated to promote adhesion to the ABS synthetic resin liner wall.
The problem addressed by the Weiss et al patent is that foamed-in-place insulation tends to adhere to the liner wall which is conventionally formed of a synthetic resin. Because of temperature changes, stress cracking of the liner often results both from propagation of stress cracks developed in the foam to the liner wall and from the differential thermal expansions of the foamed insulation and the liner wall material. A common proposed solution to this problem has been to apply a foam release agent to the liner wall. This procedure, however, is relatively expensive as it requires additional steps in the manufacturing process involving relatively expensive labor.
It has become conventional in refrigeration apparatus cabinets to form the outer wall, or shell, of prepainted sheet metal. The use of such prepainted material effectively precludes the welding of the corners of the cabinet because of the discolorations caused by said welding. The use of less rigid joint means results in a substantially less rigid outer shell structure. While the foamed-in-place insulation sets up to define a rigid body, the fact that there is only limited adhesion between the outer surface of the liner wall and the foamed-in-place insulation precludes the provision of a double-stressed skin laminate system. There has not heretofore been a completely satisfactory solution to the problems resulting from utilizing prepainted panels in such cabinets.